The present invention relates generally to a system and method for engine-bay cooling in a turbojet aircraft engine along with cycle flow matching. More particular, the present invention utilizes the structure of a decoupled third stream inlet duct on a decoupled third stream annulus (“DTSA”) aircraft gas turbine engine to modulate intake airflow between the inlet decoupled inlet duct and an engine bay cooling stream.
Supersonic aircraft endure extreme high temperatures caused by propulsion systems and in-flight engine cooling is required. Many aircraft engine cooling systems employ the use of external apertures to intake cooling airflow from one or more parts of the aircraft. Such external apertures are not desirable for achieving a low observable (“LO”) signature for the aircraft. Furthermore, the use of additional apertures increase complexity, cost and weight of the aircraft requiring additional mechanical systems such as additional flow paths and mechanism to draw the cooling external airflow to an engine bay.
Furthermore, variable geometries for inlets systems for cycle matching are common in supersonic aircraft. The objective of the variable geometries are to vary the airflow intake to match the airflow the engine requirements at varying speeds, engine loads and altitudes. Such variable geometries add weight, cost and complexity to the intake system. In many fixed geometry intake systems, in order to reduce weight and complexity, such systems may operate in a preferred range of cruising altitude and Mach number. In off-design operating conditions, however, the aircraft suffers from performance penalties caused by spillage drag of supplying too little or too much airflow to the aircraft engine.
As such, there is a great need in the art for an aircraft engine airflow management system that can provide engine bay cooling while maximizing the LO of the aircraft. In addition there is a great need in the art for an engine intake airflow management system that provides a simplified cycle matching that reduces the weight and complexity of existing systems.